The present exemplary embodiment relates to controlling edge thickness of an article of manufacturing. It finds particular application in conjunction with the manufacturing of coated sheets, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Coatings may be applied to a moving substrate using application methods such as curtain coating, roller coating, flow coating, or spraying. During such processes, methods have been developed to create uncoated edges along the substrate. For example, a curtain coater may include a device called an interrupter cup which can be used to create an edge and also control the width of the uncoated area. In the case of a roofing membrane, such an uncoated area of a web process can form the “selvage edge”.
As for coating asphalt shingles, the control and the formation of a predetermined edge is advantageous for applying the coating in certain areas of the shingle and not in other areas. For example, distinct portions of a coating may be applied on top of a layer of granules. In one embodiment, the coating may be a clear coat that is desired to be applied to that portion of the granules which will be visible once the shingles are applied to a roof. The clear coat having a well defined edge will assist with appearance of the shingle, as well as the overall roof appearance. The well defined edge will also reduce cost and increase productivity in the manufacturing of such shingles.
Unfortunately, a well-defined uniformly thick coating with a clean edge is difficult to achieve. Applicant has become aware that surface tension driven flow and edge evaporation effects will result in the formation of a thicker edge also known as a beading edge (picturing framing effect) on the film formed by the cured coating. The thicker coating along the edge of the coating creates coating curing issues due to the extra thickness of coating. Also, a beading edge on the final product can interfere with the normal use of the product. For example, the beading edge along the selvage edge of a roofing membrane can prevent good adhesion during the lapping process and it also has an aesthetically unacceptable appearance. As for asphalt shingles, a beading edge on the shingle can create high spots for water, dirt, or other contaminants to accumulate. The beading edge can also interfere with sealing the adjoining shingles. Furthermore, if the beading edge is exposed, it could very likely create appearance problems.